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Citrus Greening (Huanglongbing): A Serious Threat to the Florida Citrus Industry1

J. D. Burrow, M. M. Dewdney, T. Vashisth, and L. M. Diepenbrock 2

This publication was designed as a trifold brochure. Click here to view in brochure format (pdf, 375 KB)

Huanglongbing History

  • In 1995, the official name for greening became Huanglongbing (HLB)

  • The vector, Asian citrus psyllid, was first found in Florida in 1998

  • HLB was first detected in residential areas in South Florida in August 2005

  • As of October 2006, HLB affected trees had been found in twelve counties

  • By October 2007, affected trees had been discovered in twenty-eight counties

  • Thirty-two counties had confirmed greening in their area by the end of 2008

  • By February 2010, thirty-four counties had at least one positive confirmed HLB affected tree

  • HLB is now confirmed in all commercial citrus growing counties in Florida

  • Currently, identified in most non-commercial citrus growing counties in residential properties

Huanglongbing Biology

  • A disease caused by a phloem-limited bacterium affecting all citrus cultivars

  • The rod-shaped, Gram-negative bacterium is named Candidatus Liberibacter asiaticus

  • Bacterium does not move between trees without the insect vector or through grafting

  • The bacteria are present in symptomatic tissues in low numbers

  • Phloem tissue is damaged when bacteria are present

  • Starch accumulates to toxic levels in plant cellsExcessive phloem tissue is produced in infected trees

  • Bacteria are at their highest levels in young asymptomatic tissues and appear to die as tissues age and become symptomatic

  • Changes to the plant tissue begin in the early infection before symptoms

Varieties Affected

  • All citrus varieties and rootstocks can be affected by HLB

  • Affects plants in the Rutaceae family (ex. box orange and orange jasmine)

Greening Vector

  • Asian citrus psyllid (Diaphorina citri)

  • Five nymphal stages

  • Numerous generations per year

  • Egg to adult in 2 weeks at 75°F to 85°F

  • Egg stage lasts an average of 3 to 4 days

  • Duration of the nymphal stages is about 12 to 14 days at 82°F

  • Adult psyllids may live for several months in cool temperatures

  • Psyllids can acquire the bacterium from infected trees, regardless of whether symptoms are present on the tree

  • The longer psyllids remain uncontrolled and are allowed to feed on infected trees, the higher the chance that those psyllids will acquire and spread HLB to other trees

  • Psyllid populations are best managed by controlling adults prior to the presence of new flush which facilitates rapid population growth

  • Chemical control of the psyllid and removal of infected trees are the only methods currently available to manage the spread of greening

Commercial Management

Residential Management

  • Remove infected trees

  • Use of disease-free nursery trees (a certified nursery tag should be attached to tree at time of purchase)

  • Use horticultural oil sprays to manage psyllid populations

  • When applying pesticides, remember the label is the law

  • The Florida Department of Agriculture has a release program for the Tamarixia radiata, a beneficial insect of the psyllid. For more information, visit https://www.freshfromflorida.com/

Greening Symptoms

  • Symptoms can be found year round, but are more prominent September through March

Figure 4. Vein corking
Figure 4.  Vein corking

Figure 5. Fruit remain green at the blossom end
Figure 5.  Fruit remain green at the blossom end

Figure 6. Yellow Shoots
Figure 6.  Yellow Shoots

Figure 7. Yellow veins
Figure 7.  Yellow veins

Figure 8. Reduced fruit size
Figure 8.  Reduced fruit size

Figure 9. Blotchy mottle—key diagnostic symptom
Figure 9.  Blotchy mottle—key diagnostic symptom

Diagnostics

Southern Gardens Diagnostic Laboratory

111 Ponce de Leon Ave.
Clewiston, FL 33440
(863) 902-2249
Contact: Mike Irey
msirey@ussugar.com

Florida Division of Plant Industry

PO Box 147100
Gainesville, FL 32614-7100
(800) 282-5153

UF Plant Diagnostic Center

Building 1291, 2570 Hull Rd.
Gainesville, FL 32611
352-392-1795

Before sending samples, contact the testing facility to obtain proper sampling procedures, submission guidelines, and fees.

Contacts

UF/IFAS Citrus Research and Education Center

Jamie Burrow
Extension Program Manager
863-956-8648
Megan Dewdney, Ph.D.
Plant Pathologist
863-956-8651
Tripti Vashisth
Horticulturist
863-956-8846
Lauren Diepenbrock, Ph.D.
Entomologist
863-956-8801

UF/IFAS Indian River Research and Education Center

Rhuanito "Johnny" Ferrarezi, Ph.D., Horticulturist
772-577-7376
Liliana Cano, Ph.D., Plant Pathologist
772-577-7350
Jawwad Qureshi, Ph.D., Entomologist
772-577-7339

UF/IFAS Southwest Florida Research and Education Center

Ute Albrecht, Ph.D., Plant Physiologist
239-658-3422
Fernando Alferez, Ph.D., Horticulturist
239-658-3426
Ozgur Batuman, Ph.D., Plant Pathologist
239-658-3408
Phil Stansly, Ph.D., Entomologist
239-658-3427

UF/IFAS Extension Offices with Citrus Agents

Hardee, Hendry, Highlands, Lake, Polk, St. Lucie, Sumter

Websites

UF/IFAS Extension Citrus Agents
http://citrusagents.ifas.ufl.edu
UF/IFAS Citrus REC
http://www.crec.ifas.ufl.edu
UF/IFAS Southwest Florida REC
https://swfrec.ifas.ufl.edu/
Local UF/IFAS Extension Office
http://sfyl.ifas.ufl.edu/find-your-local-office/

For more information, please contact the UF/IFAS Citrus Research and Education Center, Lake Alfred 863-956-1151

Footnotes

1. This document is CH198, one of a series of the Horticultural Sciences Department, UF/IFAS Extension. Original publication date July 2008. Revised July 2009, March 2014, and June 2018. Visit the EDIS website at https://edis.ifas.ufl.edu.
2. J. D. Burrow, Extension program manager; M. M. Dewdney, associate professor, Department of Plant Pathology; T. Vashisth, assistant professor, Horticultural Sciences Department; and L. M. Diepenbrock, assistant professor, Department of Entomology and Nematology; UF/IFAS Citrus Research and Education Center, Lake Alfred, FL 33850.

*T.M. Spann, former associate professor, Horticultural Sciences Department